Spacecraft or satellite attitude control requires periodic use of thrusters to maintain or change spatial positioning. Because of severe restrictions in weight and size in spacecraft and satellites, it is important to provide very small thrusters capable of delivering small, precisely metered, controllable amounts of propellant in order to allow exact position control of satellites, especially small satellites. Many existing thrusters are cold gas thrusters, the gas propellants of which are stored under extremely high pressure in order to provide an adequate quantity of propellant, especially when the mission of the satellite is expected to be lengthy. The propellant is stored in relatively large and heavy tanks because of the high pressure. Additionally, the valves used to precisely meter the gases to the thruster nozzle are necessarily quite large and heavy as well, and usually comprise solenoid-operated on-off valves having carefully machined, and therefore expensive, components.
For smaller spacecraft and satellites, relatively low thrust may be required for, for example, three-axis positioning systems. Recently there has been an interest and significant activity in the design and use of microthrusters. Since the spacecraft or satellites that the microthrusters control are quite small, and space and weight are at a premium even with respect to larger craft and satellites, the thrusters must be exceptionally small and light as well, although capable of delivering thrust on the order of 1*10−6 lb. to 0.005 pounds or so. Larger spacecraft and satellites require larger thrusters.
Accordingly, it is desirable to provide a thruster that is both lightweight and small. In addition, it is desirable to provide a thruster having a valve and metering system that is small, lightweight, and relatively inexpensive to manufacture. Also it is desirable to provide a thruster having a valve that can be scaled to accommodate a number of different thrust requirements. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.